Flexible fuel internal combustion engines are fuelled with one or more fuels. These engines can operate in a dual fuel mode where the engine is simultaneously fuelled with two different fuels. Alternatively or additionally, these engines can operate in a bi-fuel mode where the engine is configured to fuel with the two different fuels but only operates with one of these fuels at a time.
Conventional engines fuelled with liquid fuels (gasoline, diesel, ethanol etc.) include control systems (OEM control systems) in engine control units (ECU) that monitor and control engine operation and the introduction of the liquid fuels. Sensors monitoring various engine parameters provide signals to these OEM control systems that are input into algorithms that control engine performance. The algorithms output signals to control various actuators and fuel injectors to maintain certain engine parameters within predetermined thresholds. The OEM control systems have evolved over several decades and comprise advanced control techniques. These engines are being adapted to be additionally or alternatively fuelled with gaseous fuels (natural gas, liquefied natural gas, liquid propane gas, etc.), operating in the dual-fuel and/or bi-fuel modes.
Gaseous fuel control systems govern the delivery of gaseous fuel to fuel injectors and command these fuel injectors to introduce a predetermined quantity of gaseous fuel at a specific timing into intake air systems and/or combustion chambers. Sensors monitoring various parameters of a gaseous fuel supply system provide signals to the gaseous fuel control system representative of these parameters, and together with other engine parameters are input into algorithms that control engine performance and output signals to control various actuators and fuel injectors to maintain certain engine parameters within predetermined thresholds. The gaseous fuel control system comprises advanced techniques for controlling the combustion of gaseous fuel such that the demanded power and speed are met and emissions are maintained below predetermined thresholds.
U.S. Pat. No. 8,498,799, issued Jul. 30, 2013 to Matthews et al., the '799 patent, discloses a technique for controlling fuel injection in engines configured to operate using different fuels. An engine control module (ECM) controls the engine and also calculates a first fuel mass of a first fuel and a second fuel mass of a second fuel. The first fuel mass is introduced by a first fuel injection system that is commanded by the engine control module. The second fuel mass is introduced by a second fuel injection system that is commanded by a second control module. The second control module commands fuel injectors and other components in the second fuel injection system. Although the second control module can determine pulse widths used to actuate the fuel injectors based on the second fuel mass received from the first control module, the second control module does not comprise any algorithms for determining the quantity of the second fuel to be introduced or the timing at which the second fuel is introduced by the second fuel injection system.
United States Patent Publication No. US 2013/0103286, published on Apr. 25, 2013 by Guido et al., the '286 patent publication, discloses a technique of supplying fuel to an engine via multiple fuel paths. A controller receives signals from various sensors coupled to the engine, representative of conventional engine parameters, and commands second fuel injectors. A secondary controller receives pulse width information from the controller over a communication bus that it uses to actuate first fuel injectors. The first and second fuel injectors may be supplied with the same type of fuel, or different types of fuel. The secondary controller receives signals from temperature and pressure sensors employed to monitor a fuel that is introduced by the first fuel injectors, and can provide a signal to a fuel gauge. The controller broadcasts injector pulse widths, start of injector opening timing and/or stop of injector opening timing to the secondary controller that employs this information to actuate the first fuel injectors.
The second control module of '799 and the secondary controller of '286 can actuate gaseous fuel injectors in a multi-fuel engine. However, neither of these controllers comprises a gaseous fuel control system that determines the quantity of gaseous fuel and timing at which that quantity is introduced by gaseous fuel injectors.
A flexible fuel control system for a conventional liquid fuel and an alternative gaseous fuel comprises an OEM control system and a gaseous fuel control system. Each engine manufacturer has its own OEM control system designed for conventional liquid fuel operation that comprises different and/or proprietary algorithms that must interface and interoperate with a gaseous fuel control system in a flexible fuel control system. There is a need for a flexible fuel control system that reduces the changes required in each OEM control system in order to operate with a gaseous fuel control system.